Bone marrow failure, myetodysplasia (MDS), and acute myelogenous leukemia (AML) are the most prevalent life-threatening complications of Fanconi anemia (FA). While the onset and severity of hematopoietic disease varies from case to case, it is found in virtually all complementation groups, suggesting that each wild-type FA protein may have a specific function in hematopoietic cells. Work carried out in our laboratory during the past funding period has confirmed this notion for the FANCC protein. A major objective of this project is to test the hypothesis that other FA proteins (namely FANCA, FANCG, and FANCD2) are similarly multifunctional and have important survival functions beyond those linked with damage induced by cross-linking agents. While strong evidence exists for a nuclear function of FANCC, which participates in a nuclear complex that probably facilitates DNA unwinding and repair, we find that FANCC also functions to modulate the state of activation of pro-apoptotic signaling molecules (e.g. the eiF2alpha kinases PKR and PERK). Because the capacity of FANCC to Suppress eiF2alpha kinases is defined by its capacity to bind the chaperone hsp70, we believe that FANCC functions as an anti-apoptotic co,chaperone in norrnal cel!s, This hypothesis will be tested:in aim 1. We also discovered that in response to H2O2, FANCA and FANCC facilitate the activation of STAT3 and FANCG and FANCD2 facilitate activation of STAT5. In aim 2 we test whether the same will hold true for STAT responses induced by hematopoietic growth and survival factors in hematopoietic stem cells and progenitors. We have also reported that neoplastic clones arising in the marrow of FA patients have acquired the capacity to resist apoptotic cues to which non-neoplastic FA cells are hypersensitive. We reason that such clones arise adaptively by somatic mutations that either bypass a requirement for FANCC dependent STAT activation or by suppressing elF2alpha kinases (Aim 3). Based on these observations, we propose to test three related hypotheses:(1) the co-chaperone function of FANCC suppresses activation of pro-apoptotic eiF2alpha kinases and requires intact FANCA, FANCD2 and FANCG (Aim 1), (2) FANCC functions as a co-chaperone to facilitate traffic and activation of STAT 1, 3 and 5 molecules in response to growth and survival factors and to H2O2 and requires the presence of wild-type FANCA and FANCG (Aim 2), and (3) somatic mutations leading to neoplastic clonal evolution in FA hematopoietic and epithelial stem cells are precisely those that overcome the pro-apoptotic state of non-neoplastic FA cells (Aim 3). This application is designed to test these hypotheses.